Rodent Poison Found in Two Dead Southern California Mountain Lions

What to Know

Mountain lions P-30 and P-53 were found dead in the Santa Monica Mountains. Both had ingested similar poisons

Since 2002, NPS researchers have found the poison’s compounds in 23 out of 24 SoCal mountain lions tested

Vehicles strikes remain the most common cause of death for Southern California’s mountain lions

One of two mountain lions found dead recently in the Santa Monica Mountains was killed by potent chemicals used to poison rodents, according to the National Park Service.

The mountain lion, known as P-30, is the fifth big cat in a long-term study of the species whose death was connected to the rodent poison. An otherwise healthy 6-year-old male cat, P-30’s official cause of death was anticoagulant rodenticide poisoning, NPS biologists said.

The cause of death for a second mountain lion found dead in August in the Malibu area not been determined, but similar poisons were found in her system, the NPS said.

The body of P-30 was found by researchers after his radio collar sent a mortality signal from the Topanga State Park area. His carcass showed no obvious signs of injury, according to the NPS.

National Parks Service

A necropsy determined he suffered internal bleeding, and hemorrhaging of the brain and abdominal cavity, which contains crucial organs. Testing showed P-30 had five different rodenticides in his system, including a high concentration of the potent anticoagulant bromadiolone.

The big cat’s death is another example of the wide-ranging impacts that rodenticides, intended to control pests can have on wildlife. Since 2002, when a study began to examine how the animals survive in an urban area, NPS researchers have found the poison’s compounds in 23 out of 24 SoCal mountain lions tested.

The poisoned mountain lions include a 3-month-old kitten.

“Just about every mountain lion we’ve tested throughout our study has had exposure to these poisons, generally multiple compounds and often at high levels,” said Seth Riley, an ecologist and the wildlife branch chief for Santa Monica Mountains National Recreation Area (SMMNRA). “A wide range of predators can be exposed to these toxicants — everything from hawks and owls to bobcats, coyotes, foxes, and mountain lions.

“Even if they don’t die directly from the anticoagulant effects, our research has shown that bobcats, for example, are suffering significant immune system impacts.”

Researchers said mountain lions are likely exposed through secondary poisoning, such as eating another animal that ingested the poison used for bait.

Vehicles strikes remain the most common cause of death for Southern California’s mountain lions, followed by anticoagulant poisoning.

P-30 was considered a significant part of the NPS mountain lion study. Re-captured and fitted with a new GPs collar in February 2018, he was the first male kitten to be marked at his den, then survive to adulthood and establish a home range — an area typically traveled in search of food and a mate.

P-53 was a 4-year-old female mountain lion who was found dead Aug. 15 in Malibu. Her carcass was too decomposed to determine a cause of death, but substances similar to those found in P-30 were found in her liver, the NPS said.